Dendritic NiS2@Co–N–C nanoarchitectures as bifunctional electrocatalysts for long-life Zn–air batteries

Abstract

Zn–air batteries (ZABs) have been widely studied due to their high theoretical energy density, low cost, and high safety. However, the lack of efficient bifunctional electrocatalysts toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hinders their large-scale application. Herein, a dendritic NiS₂@Co–N–C/CNF nanoarchitecture is proposed, which was fabricated by high-temperature carbonization of Co-MOFs and a subsequent simple hydrothermal composite method using NiS₂ nanosheets. The catalyst is reasonably designed to integrate the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) active sites on the surface of carbon nanofibers. Through the synergy between NiS₂ and Co–N–C/CNF and the unique branch–leaf porous structure, the catalyst showed excellent catalytic activity and stability. In an alkaline electrolyte, the OER overpotential of NiS₂@Co–N–C/CNF is 300 mV at 10 mA cm⁻². The ORR half-wave potential (E_1/2) of NiS₂@Co–N–C/CNF is 0.8 V. In addition, the superior catalytic activity of NiS₂@Co–N–C/CNF could be transferred to a ZAB, which exhibits a maximum peak power density of 181 mW cm⁻² along with an ultra-long cycling stability for 1050 and 600 h at discharging current densities of 5 and 10 mA cm⁻², respectively. The performance is significantly higher than that of commercial precious metal Pt/C + IrO₂ mixed catalysts. The peak power density of solid state ZAB (SSZAB) integrated with NiS₂@Co–N–C/CNF is 76 mW cm⁻², and it can still maintain excellent cycling stability under different bending states. More impressively, four in-series SSZABs (NiS₂@Co–N–C/CNFs) can charge smartphones, indicating their potential feasibility in the field of wearable electronics.